1. Field of the Invention
The present invention relates to a mobile information terminal, more particularly a mobile information terminal provided with a security system for protecting data held inside. Further, it relates to a security method and a storage medium storing a security program for the same.
2. Description of the Related Art
As the above mobile information terminal, there are mobile phones, personal digital assistants (PDAs), etc. The following explanation will be given with reference to a mobile phone as a representative example.
Due to the increasing sophistication of functions of mobile phones in recent years, their data storing units are now storing huge amounts of a large variety of data. This also includes important data requiring secrecy. Therefore, if a mobile phone happens to be lost, it is necessary to protect the legitimate user of that mobile phone from theft of that important data etc. by malicious third parties. That is, the security of the above important data has to be secured.
Various methods have been proposed in the past for securing data security. For example, there are Japanese Patent Publication (A) No. 2006-109326, Japanese Patent Publication (A) No. 2002-325280, Japanese Patent Publication (A) No. 2000-276247, and Japanese Patent Publication (A) No. 2002-330220. Japanese Patent Publication (A) No. 2006-109326 discloses a transponder with a built-in RFID tag paired with a mobile phone as a mobile identification means.
Further, Japanese Patent Publication (A) No. 2002-325280 uses a status detecting means for detecting the state when the mobile phone is stolen. This status detecting means finds the location, detects acceleration, detects vibration, or detects inclination.
Further, Japanese Patent Publication (A) No. 2000-276247 judges if a mobile phone is in range enabling communication with a relay station and, when judging that it is in range, turns on the power of the mobile phone to set it into a usable state.
Still further, Japanese Patent Publication (A) No. 2002-330220 uses a specific data transmitter within a predetermined range of distance paired with a mobile phone holding its own specific data, compares specific data received from that specific data transmitter and that own specific data, and judges the mobile phone is lost or stolen and issues an alarm when they do not match.
Summarizing the problems to be solved by the invention, according to the method of Japanese Patent Publication (A) No. 2006-109326, a transponder is required in addition to the mobile phone, so the cost becomes higher and the two devices have to be simultaneously carried and therefore the user is inconvenienced. The same is true for the method of Japanese Patent Publication (A) No. 2002-330220. Further, according to the method of Japanese Patent Publication (A) No. 2000-276247, the only condition for judging theft is whether the phone is “in a communicable range”. It is therefore difficult to determine if the phone has really been stolen.
On the other hand, the method of Japanese Patent Publication (A) No. 2002-325280 is similar to the present invention explained later in detail in the point of introducing a status detecting means. However, as the status detecting means in Japanese Patent Publication (A) No. 2002-325280, a global positioning system (GPS) device, acceleration sensor, posture angle sensor, etc. is envisioned. A mobile phone including any of these becomes larger in size.